In order to conserve energy, automobiles are now being engineered to give improved mileage compared to those in recent years. This effort is of great urgency in the United States in view of regulations which compel auto manufacturers to achieve prescribed mileage. In an effort to achieve the required mileage and fuel economy, new cars are being down-sized and made much lighter.
EP 0 020 037 discloses that the use of an oil-soluble, C12-36 aliphatic hydrocarbyl succinimide or succinimide provides a friction reducing effect when it is incorporated into a lubricating oil, such as for use in a crankcase. The hydrocarbyl succinic anhydride is reacted with ammonia to form the succinimide. The reference discloses that the succinimide can also be used in both diesel fuel and gasoline. However, the reference does not teach that the succinimide can be used in low-sulfur fuel compositions. In fact, the reference is silent with respect to low-sulfur fuels.
Another way to improve fuel economy is to reduce engine friction.